Best Fitting Probability Distributions of Monthly Rainfall Extremes in Nasiriyah City, Southern Iraq

الملخص

Analysis of rainfall data is important in the design and planning of water projects in cities. Therefore, in this research, rainfall data recorded at the Nasiriyah station located in the center of Thi-Qar Governorate, southern Iraq, was used for 80 years for the period (1940-2020) to determine the best probability distribution fits this data. All tests and statistical analyzes were carried out using the (HYFRAN-PLUS version 1.2) software, and the method of maximum likelihood was applied to obtain the coefficients of theoretical distributions. Eight distributions were tested: GEV, Gumbel, Weibull, Normal, Lognormal, Gamma, Pearson type 3, and Log-Pearson type 3, and adequacy test was conducted by (Chi-Square) test for these distributions, the results showed the GEV, Lognormal, Pearson type 3, and Log-Pearson type 3 distributions are suitable, for describing extreme monthly rainfall in this study area.